Although recently, several kinds of pharmaceutical composition have been proposed and put into practical use, almost of them exhibit side effects such as leukocytopenia, alopecia and gastrointestinal disturbances. Accordingly, in actual fact, their application is restricted to an extent.
More recently, the application of a substance obtained by chemically bonding an antibody to tumor (cancer) antigen [hereinafter referred to an antitumor-antibody (anti-cancer-antibody)] with an antitumor substance (anti-cancer drug), as an anti-tumour agent, has been tried. However, since the antitumor-antibody (anti-cancer-antibody) used for such a substance is not sufficiently purified, to remove general immunoglobulin and so it could not be recognized as a pure antitumor-antibody (anti-cancer-antibody). Accordingly, in the case where such a substance obtained by bonding such an antitumor-antibody (anti-cancer-antibody) with an antitumor substance (anti-cancer drug) is administered as an anti-tumour agent, the occurrence of pyrexia and anaphylactic shock caused by immunoglobulin contained in the above-mentioned antitumor-antibody (anti-cancer-antibody) is inevitable.
The inventors taking into consideration of the above-mentioned technical backgrounds have examined the elimination of side effects observed in the use of antitumor-antibody (anti-cancer-antibody) and as a result, have confirmed that the extremely pure antitumor-antibody (anti-cancer-antibody) is obtained by purifying the immunoglobulin fraction of the antiserum with an affinity-chromatographic technique and that a pharmaceutical composition obtained by bonding the above-mentioned purified antibody to an antitumor substance (anti-cancer drug) having at least one amino group or carboxyl group does not exhibit the above-mentioned side effects.
Accordingly, an object of the present invention is to supply a pharmaceutical composition having low cytotoxicity and on the other hand excellent antitumor activity (especially, anti-cancer activity). Also an another object of the present invention is to supply an antitumor-antibody (anti-cancer-antibody) with a high purity and a method for preparing the same.